1. Field of the Invention
The present invention relates to a levitation heating method and levitation heating furnace to be employed for a microgravity material manufacturing test which is made for manufacturing materials such as a semiconductor material and an alloyed material under the space environment.
2. Description of the Prior Art
FIG. 10 is a block diagram showing an arrangement of a conventional ring-shaped electrode type electrostatic levitation furnace such as is disclosed in U.S. Pat. No. 4,521,854 "CLOSED LOOP ELECTROSTATIC LEVITATION SYSTEM" (Jun. 4, 1985). In the illustration, numeral 1 represents dish-type electrodes concaved downwardly and arranged in confronting relation to each other, 2 designates a specimen placed between the dished electordes 1, 3 depicts a CCD camera for measuring the position of the center of gravity of the specimen, 2, 4 denotes a control circuit coupled to the CCD camera 3, and 5 is a high-voltage power source coupled to the electrodes 1 and the control circuit 4.
The conventional ring-shaped electrode type electrostatic levitation heating furnace has the above-described arrangement and levitates the specimen using electrostatic force. For heating the specimen 2, any heating device is limited because of the effects of non-convection and uniform diffusion under microgravity conditions. For example, electron beam heating causes interference with the electrostatic field. Further, the laser causes concurrent enlargement of the apparatus, and results in heating of only a portion of the surface of the specimen a. Induction heating also causes interference with the electrostatic field and cannot be employed for heating conductive materials. Similarly, a halogen lamp or xenon lamp cannot uniformly heat the specimen 2 and has an extremely short lifetime of about 100 hours. Accordingly, with the above-described problems, all the conventional heating means are unsuitable for the electrostatic levitation furnace. Hence, there is no appropriate heating means which is capable of making a uniform temperature distribution on the surface of the specimen, suppressing Maragoni convection and providing uniform diffusion.